Regulation of Plant Growth & Development

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In the photoperiodic control of flowering in Arabidopsis thaliana, a long-day plant, the key transcription factor CONSTANS (CO) gene, which is a main activator of the florigen FT gene, is mainly regulated by the circadian rhythms and modulated by light-signaling transcriptionally and post-transcriptionally. In rice, a shrot-day plants, it has been revealed that Heading date 1 (Hd1) gene (a CO otholog) controls Heading-date 3a (Hd3a) gene (a FT ortholog). Therefore, it is now thought that the difference between long-day and short-day plants can be explained by rather simple modification of the evolutionally conserved CO-FT (Hd1-Hd3a) transcriptional regulation system. Recent cloning of novel flowering-time genes in rice, however, strongly suggests that there may be unique systems to control flowering in rice. Here, I would summarize the new knowledge on novel flowering-time genes in rice to discuss the difference of molecular machinery between short-day and long-day plants.

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Endoreduplication (or endocycle) is a modified cell cycle, that widely seen among multicellular organisms such as plants and animals. In plants, endoreduplication is under developmental or environmental controls and results in extensive increase of cell volume and therefore affects plant body size. Arabidopsis thaliana, the most widely studied model plant, exhibits endoreduplication in nearly all organs at high levels, and thus is a useful material to study the biological significance and molecular mechanisms of endoreduplication. In this review, I will overview the present understandings of the endoreduplication in Arabidopsis, with a special emphasis on the generality of this biological process.

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This report describes the development of jasmonic acid biosynthesis inhibitor in our laboratory. We designed the jasmonic acid inhibitor targeting on the allene oxide synthase (AOS) and structure-activity relationships studies revealed a potent inhibitor, JM-8686, with an IC_<50> value of approximate 10nM in an in vitro assay. Kinetic analysis of JM-8686 indicated it was a competitive inhibitor of AOS. Stereochemical structure-activity relationship studies indicated that the potency of (R)-(-)-JM-8686 was about 200 times of that of (S)-(+)-JM-8686, with an IC_<50> value of approximate 5nM and 1,000nM, respectively.

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